October 24, 2004 -- Aspiring actor Sam Kellerman left his beloved New York to make it big in Los Angeles, but his loyalty to a down-and-out pal from his youth may have cost him his life.

Despite his upper-middle-class Manhattan pedigree, the 29-year-old brother of Fox Sports Network anchor Max Kellerman dabbled in New York City street life as a teenager — boxing, rapping and donning inner-city fashions.

Years later, many of those endeavors were abandoned and forgotten, but he never cast aside the people he met along the way.

One of them was troubled prizefighter James "The Harlem Hammer" Butler, 31, who was charged last week with the brutal murder of his devoted friend, after Sam was found battered in his Hollywood apartment.

A friend of the Kellermans told The Post that Butler showed up several weeks ago in Los Angeles, where Sam had been living for a year and half, claiming his apartment in Florida had been destroyed by hurricanes and that he had a scheduled bout in California.

Not wanting to disappoint an old friend, Kellerman took him in, but over the next two weeks began fearing that Butler may have gone off medication used to control his bipolar disorder.

"Sam really wanted him out, but at the same time felt bad for him," said a friend of Kellerman's. "[Butler] had no other friends, and he told me everyone else had left his life."

One friend suspects that the fight that ended Kellerman's life may have been triggered by an argument over when he should move out.

Max Kellerman told The Post: "Though it would seem that Sam's fate suggests no good deed goes unpunished, Sam's life did not suggest that at all.

"It was full of good deeds. Sam believed that life came with the responsibility of empathy and kindness."

A regular contributor to foxsports.com, Sam Kellerman had been making inroads into acting, recently appearing in a British TV commercial for mobile phones with Christina Aguilera.

Kellerman had also had a bit part on a promotional spot for New York's bid to score the 2012 Olympic Games.

Although Sam and Max Kellerman grew up in Greenwich Village as sons of a New York psychoanalyst, they had a fascination with boxing and gritty urban culture.

Both the Kellerman brothers were recreational boxers and began hanging out in 1992 at Gleason's Gym and the now-defunct Times Square Gym, where young wannabes mingled with seasoned pros.

Butler, then an up-and-coming amateur standout, took on a quasi-coaching role with Sam, sparking a friendship that lasted into adulthood.

The Kellerman brothers once even made a rap video called, "Rumble Young Man, Rumble," which included Butler.

Years later, Sam would recruit Newbold for a production of Shakespeare in Washington Square Park, with proceeds going to the victims of 9/11.

"He was a special angel," said Meegan Kelso, Sam's friend and talent agent. "He got people. He got that they need to be unconditionally loved despite their flaws. I've not known anyone with such a huge heart."

Opening his small home to Butler was far from the first selfless act shown by Sam Kellerman to the fighter.

Once an amateur standout, Butler fell on hard times after sucker-punching Richard Grant at the completion of their match at the Roseland Ballroom in 2001 — on a fight card that was to benefit the families of 9/11 victims.

Butler was taken from the ring in handcuffs and spent four months on Rikers Island for the assault.

While most of the boxing community shunned Butler in disgust, both Sam and Max Kellerman remained loyal to the pug they had known as a teenager in New York.

Sam visited the jailed fighter and wrote a sympathetic article for foxsports.com about The Harlem Hammer's battle with bipolar disorder.

Kellerman had no idea how prophetic and tragic his column would be.

"It's painful. It hurts man," Butler told Kellerman, according to the article. "It's even physically draining. And you also end up hurting people you love. They try to help you, and you flip on them for some small thing." He also indicated back then that he was aiming to go off the medication.

"I've taken the classes, read the books. I know what to do," Butler told Kellerman. "You can reach a level where you don't need the medication anymore, you just have to be strong-minded."

"Through all his troubles, the Kellerman brothers always stood by him. They have really good hearts," said LAPD Detective Elizabeth Estupinian. "The Kellermans always gave him a second chance and it's really tragic."

After getting out of jail, Butler moved to Florida and made a comeback in January with legendary Vero Beach-based trainer James "Buddy" McGirt.

But Butler struggled in his comeback bid winning only two of his four post-Grant fights.

He and McGirt split shortly before his last fight, a decision loss to light-heavyweight contender, Omar Sheika, in Newark.

The trainer said his split with Butler was amicable, because McGirt simply needed to spend more time with another, championship fighter.

"When he was down here, everything was fine. I don't know what happened when he left," McGirt said.

"I didn't even know he was in California. I had no problems with him at all. He had a lot of potential. He was his own worst enemy. He was hard on himself."

But it seems that when Butler re-entered Sam's life in Los Angeles, he lied when making his appeal for a bed by claiming he had a bout in California. The California Athletic Commission had no record of a scheduled fight for Butler, who did not even have a Golden State boxing license.

A promoter for light-heavyweight champ Julio Cesar Gonzalez said Butler was briefly considered for a match, but was passed over in early October.